The invention relates to a passively cooled blade platform for a gas turbine rotor with cooling channels in an inner surface thereof to direct cooling fluid flow from the surrounding relatively stationary cooling fluid.
Gas turbine engines utilize a portion of the compressed air generated by the compressor to cool engine components with compressed cooling air flow, such as through the turbine blades and blade platforms. Spent cooling air eventually rejoins the hot gas path flow and is ejected from the engine with the exhaust.
In some instances however, use of forced compressed air cooling is not possible or imposes an undesirable penalty on the engine efficiency. The invention is directed to passive cooling, as opposed to active or forced cooling flow, that results from the moving of a hot engine part within a relatively static coolant thereby creating a relative fluid flow and cooling effect. One of the applications of passive cooling is to cool the blade platform lip of a turbine blade as it rotates in a relative stationary volume of cooling air.
U.S. Pat. No. 6,065,932 to Dodd shows an example of using the rotation of the turbine to exhaust spent coolant from the underside of turbine blade platforms and prevent the accumulation of heat. In this example, the motion of the turbine is utilized to create sufficient vacuum to exhaust spent coolant and maintain a flow of coolant through the platform area.
U.S. Pat. No. 5,800,124 to Zelesky shows a forced air cooling of the trailing edge lip of a turbine blade platform using a portion of cooling air flow directed at the underside of the blade platform.
It is an object of the present invention to provide passive cooling of the blade platform to eliminate the need for forced coolant use and to extend the life of the blade platform through more efficient cooling.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.
The invention provides a passively cooled blade platform for a gas turbine rotor adapted for rotation about an axis within a stationary coolant fluid. The platform has a radially outer surface defining an annular gas path, a radially inner surface in flow communication with the coolant fluid, a leading edge, and a trailing edge with at least one cooling flow channel in the inner surface. Each channel has a flow path from a channel inlet to a channel outlet, with a tangential component at the inlet opposite to the direction of rotation and an axial component at the outlet. The flow channels are defined by ribs or pedestals extending radially inwardly from the platform inner surface to direct cooling fluid flow and create turbulence. The ribs reinforce the platform structurally, and together with the pedestals serve to dissipate heat from the platform on exposure to cooling fluid flow.